(This is paraphrased from the customer's email to me.)

On page 82 of the 890_USE_101_00 manual it indicates that the system is grounded through the RIO head processor. If the connection to the RIO head is removed, the ground is lost, but there are no signals being passed. What, then, are the consequences, if any, of not having the ground
block in the RIO line? What are the safety concerns mentioned in the write-up? When should grounding blocks be installed? Could the ground in the RIO together with the ground block create a ground loop?

 

You're right in that if there is no RIO head connected it's hard to get communications to fail through a ground problem. In the case of a hot standby system, grounding the cable would allow you to remove one of the RIO head connections. In the case of an RIO cable leaving the building, code requires that the shield be grounded at that point. In this case, an isolating ground block would be preferable.

Ground blocks mounted local to the RIO head module would not normally cause any problems with ground loops. Any more than 20 feet, though, and you're looking for trouble.